posted by BRENDAN on .
Please show the quickest way to do this question?
Amanda has 20 coins in her purse. She has only 10c,20c and 50c coins, and their total value is $5. If she has more 50c than 10c coins, how many 10c has she?
Are you in algebra using variables 'c'?
I'm not sure what you mean.
What grade are you in?
c stands for cents?
yes c stands for cents.
I got 4 x 50c = $2
2 x 10c = 20 c
14 x 20c = $2.80c
so she has 2 x 10c
Since you are in year 4, you will be able to solve this algebraically.
let the number of 10c pieces be x
let the number of 20c pieces be y
let the number of 50c pieces be (20-x-y)
10x + 20y + 50(20-x-y) = 500
4x + 3y = 50
so we need positive integer solutions for x and y
clearly x has to be between 0 and 13
after only two tries, I got
x = 2, and y = 14
number of 10c pieces = 2
number of 20c pieces = 14
number of 50c pieces = 20-2-14 = 4
check: 2x10 + 14x20 + 4x50 = 500